If you are going to cruise in 6th gear then you'll have either a 1.87 rear ratio, or a 2.35 rear gear. So that puts you at roughly 2000 rpm for 80 mph depending on tire size. Dwayne is the guy to talk to about the cam but I'm thinking you need to stay in the 250 @ 050 range if you want to drive on the freeway at less than 2000 rpm. I'm not sure what the port velocity is going to be like at 2000 rpm with the MW Victor heads even with 572 cubes to feed. That engine might not like double overdrive, you'll just have to try it and see.

The Chevy 572/620 crate engine might be something to take a look at. Chevy went with 9.6 compression and the cam is 254/264 hyd roller. I haven't tested one of those engines but I assume it would work with an OD transmission since it is designed as a street rod type engine rather than a race engine. Chevy sells the 572/620 in their "connect and cruise" package with a T56 double overdrive transmission. Maybe jump on a Chevy board and see if you can find some reviews of that camshaft with the double overdrive in a car with your weight, tire size and rear gear.